Script skew camera in game engine
There is no built-in functionality for that. However, You can setup a custom camera view matrix using a bit of Python.

import bge
scene = bge.logic.getCurrentScene()
cam = scene.active_camera
# get projection matrix
camatrix = cam.projection_matrix
#modifying the camera projection matrix by modifying the x and y terms of the 3rd row to obtain a shift of the rendered area 
camatrix[2][0] = 2*shiftx
camatrix[2][1] = 2*shitfy
cam.projection_matrix = camatrix


See this for detail.